In a treating process for a workpiece such as a semiconductor wafer or the like, an ionizer is used for discharging the workpiece being electrostatically charged. The ionizer is constructed such that a positive electrode and a negative electrode are disposed in an electrode-attaching opening at a lower surface of a housing, and a positive pulsing high voltage is applied to the positive electrode and a negative pulsing high voltage is applied to the negative electrode, as shown, for example, in the patent document 1, and thereby a corona discharge is generated so as to generate a positive ion and a negative ion from both electrodes.
The positive and negative electrodes tend to have a stain due to adhesion of dust and tend to be worn by repetition of the corona discharge. Therefore, this requires frequent cleaning and exchange of the positive and negative electrodes, and the same are detachably constructed. That is, an electrode cartridge is formed by holding a pair of the electrodes by a hollow electrode holder, and the electrode cartridge is configured to be detachably attached to the housing. The attaching method is generally configured such that the electrode cartridge is fit into the electrode-attaching opening formed in the housing, and by means of rotating the electrode cartridge by a certain angle around a center axial line thereof, an attaching projection formed in the electrode cartridge is latched to an attaching concave portion formed in the housing.
However, in this kind of ionizer, the aforementioned electrode cartridge is gradually rotated by vibration, a shock, or the like caused when in use, and there is a possibility that the projection finally drops off from the concave portion and that the same is dropped off from the electrode-attaching opening. Accordingly, so as for the electrode cartridge not to be dropped off from the housing, it is required to configure an attaching operation for the electrode cartridge to be further assured.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-108829